Spatial Organization of Signal Transduction Molecules in the NK Cell Immune Synapses During MHC Class I-Regulated Noncytolytic and Cytolytic Interactions

Abstract

The cytolytic activity of NK cells is tightly regulated by inhibitory receptors specific for MHC class I Ags. We have investigated the composition of signal transduction molecules in the supramolecular activation clusters in the MHC class I-regulated cytolytic and noncytolytic NK cell immune synapses. KIR2DL3-positive NK clones that are specifically inhibited in their cytotoxicity by HLA-Cw*0304 and polyclonal human NK cells were used for conjugate formation with target cells that are either protected or are susceptible to NK cell-mediated cytotoxicity. Polarization of talin, microtubule-organizing center, and lysosomes occurred only during cytolytic interactions. The NK immune synapses were analyzed by three-dimensional immunofluorescence microscopy, which showed two distinctly different synaptic organizations in NK cells during cytolytic and noncytolytic interactions. The center of a cytolytic synapse with MHC class I-deficient target is comprised of a complex of signaling molecules including Src homology (SH)2-containing protein tyrosine phosphatase-1 (SHP-1). Closely related molecules with overlapping functions, such as the Syk kinases, SYK, and ZAP-70, and adaptor molecules, SH2 domain-containing leukocyte protein of 76 kDa and B cell linker protein, are expressed in activated NK cells and are all recruited to the center of the cytolytic synapse. In contrast, the noncytolytic synapse contains SHP-1, but is lacking other components of the central supramolecular activation cluster. These findings indicate a functional role for SHP-1 in both the cytolytic and noncytolytic interactions. We also demonstrate, in three-cell conjugates, that a single NK cell forms a cytolytic synapse with a susceptible target cell in the presence of both susceptible and nonsusceptible target cells.

Synthetic Multivalent Ligands as Probes of Signal Transduction

“…For example, when a T cell engages with a cell presenting an antigen, the negative regulator CD45 moves to the periphery of the synapse. [76,[81][82][83] Under these circumstances, the TCR is recruited to the inner portion of the synapse. These changes in receptor positioning suggest that synapse organization affects signal transmission: These intricate, orchestrated [76] movements are believed to affect the transfer and propagation of the activating signal.…”

The human CD94 gene encodes multiple, expressible transcripts including a new partner of NKG2A/B

“…This aNKIS is a complex structure requiring ATP for formation, involvement of the cytoskeleton and lipid raft polarization. [26][27][28] To avoid killing of normal cells, inhibitory NK receptors are crosslinked by their ligands and form an iNKIS, which function as a distinct unit, outside lipid rafts, not requiring ATP or active involvement of the cytoskeleton. 29,30 One such inhibitory receptor is CD94 Full /NKG2A (and potentially CD94-T4/NKG2B).…”

Intercellular Trogocytosis Plays an Important Role in Modulation of Immune Responses

“…Similarly, cell population expressing major histocompatibility complex (MHC) class II can be described as APCs, and natural killer (NK) cells could be characterized by killer Ig-like receptors (KIR) (1). When lymphocytes come in contact with target cells, many different molecules on APC and lymphocyte slide (like CD28/CD80 and LFA-1/ICAM-1) together and form an interface which is termed as "immunological synapse" (IS) and has been observed for T (2,3), B (4) and NK cells (5). The immunological synapse, like T cell IS, is thought to be the seat of initiation of TCR signaling events (6) which lead to different lymphocyte functions such as proliferation and cytokine production.…”